Consumer electronics with flip covers, such as portable computer, electronic dictionary, portable audio/video player, flip mobile phone, generally have a main body on the bottom, which is pivotally connected with the cover body on the top, such that the cover body may swing open or close with respect to the main body. Consequently, the rotating shaft is key to the quality of the products described above. In fact, the design for a good rotating shaft shall not only demand a necessary arresting effect to prevent loose joint after repetitive operations, but also prevent abnormal sound from occurring to annoy users.
Take the in-line axial friction pivotal shaft for example; the U.S. Pat. No. 5,190,391 (corresponding to ROC Patent 73784) held by the present inventor is the most prominent example. The advantage of the axial friction lies in that packing may be adjusted to press against the elastic body and in turn to change frictional torque, avoiding the loosening effect caused by repetitive operation. However, the frictional torque remains unchanged during the rotation of the pivotal shaft. For example, the opening up of the cover (the display panel) of a notebook computer often poses a difficulty for females or children. Consequently, it is necessary to design a pivotal shaft providing an auxiliary force without scarifying the arresting and locating functions.